XML data type in SQL Server? - sql

Question

I have some unstructured data that describe setting for each devices. For e.g. for Device 1:
<ChartSetting xmlns="ChartSetting1">
<ChartSizeX>132.6</ChartSizeX>
<ChartSizeY>132.6</ChartSizeY>
<ChartType>Native</ChartType>
<BarSizeX>90</BarSizeX>
<BarSizeY>6</BarSizeY>
<DistToBar>34.8</DistToBar>
<DistToFirstLineY>17.5</DistToFirstLineY>
<MarkerDistance>120</MarkerDistance>
<DistToFirstField>18.5</DistToFirstField>
<PatchSizeX>7.5</PatchSizeX>
<PatchSizeY>9</PatchSizeY>
</ChartSetting>
However for Device 2 setting is different
<ChartSetting xmlns="ChartSetting2">
<PatchGap>1</PatchGap>
<PatchSize>5</PatchSize>
</ChartSetting>
xml data is not used for query purpose, it will be passed to the .net application that eventually send it to the devicedriver (through C++ code)
We only have four types device. So possibility of different settings is limited.
Can this kind of data be stored as typed XML that adhere to some schema? Storing as varchar will be nightmare if there are invalid settings stored.
I know xml schema collection can have multiple schema but can it confirms to only one schema.
Is there an easy way to create a schema?
Should I be using untyped XML instead?

Answer 1

You could create a DTD for the four different device types and validate your XML fragments with those DTDs, but I'd suggest you do that processing OUTSIDE of SQL Server.
If you are not going to query the XML, there isn't any reason to store it as the XML data type.
Answers to your questions:
Typed XML: you'll have to use a specific type per column (see http://msdn.microsoft.com/en-us/library/ms184277.aspx)
Create a
schema - check out (http://msdn.microsoft.com/en-us/library/ms176009.aspx) and try
something like XMLSpy if it gets too complex. Your snippets looked
small so I should think you can manage it with Notepad/++
I'd use untyped XML and validate it when it gets stored and/or retrieved

Answer 2

1.I think it's possible, if your schema collection contains 4 different schemas, the related column can contain xml that satisfies one of the schemas in collection.
2.I believe the easiest way is to let sql server create a schema for you (first create tables ChartSetting1,ChartSetting2 with desired columns - it's not necessarily, you can create SELECT that returns all columns, but using tables is easier), then
DECLARE #mySchema NVARCHAR(MAX);
SET #mySchema = N'';
SET #mySchema =#mySchema +
(
SELECT * FROM ChartSetting1
FOR XML AUTO, ELEMENTS, XMLSCHEMA('ChartSetting1')
);
SET #mySchema =#mySchema +
(
SELECT * FROM ChartSetting2
FOR XML AUTO, ELEMENTS, XMLSCHEMA('ChartSetting2')
);
CREATE XML SCHEMA COLLECTION [name] AS #mySchema;
-- we don't need these tables , drop them
DROP TABLE ChartSetting1,ChartSetting2
3.It depends. I'd say if you need constrain the XML data beyond schema validation, then it makes sense to use untyped XML. If schema validation covers all aspects of data validation, why not use it?

Answer 3

I think it is impossible create schema that conforms both XML.
Many XML editors can create XSD from XML, e.g.: Visual Studio
Typed XML vs. Untyped XML

Answer 4

XML shouldent really be stored in a databse as XML. XML is more of a transport medium than data. As you say its big and hard to query. You should store your data as data (varchar int ect) then use PATH MODE to return it back to you in the format you want